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2821 = 71331
BaseRepresentation
bin101100000101
310212111
4230011
542241
621021
711140
oct5405
93774
102821
112135
121771
131390
141057
15c81
hexb05

2821 has 8 divisors (see below), whose sum is σ = 3584. Its totient is φ = 2160.

The previous prime is 2819. The next prime is 2833. The reversal of 2821 is 1282.

2821 is nontrivially palindromic in base 12.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 3-Lehmer number, since φ(2821) divides (2821-1)3.

It is a cyclic number.

It is a Carmichael number.

It is not a de Polignac number, because 2821 - 21 = 2819 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a deceptive number, since it divides R2820.

2821 is a lucky number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 76 + ... + 106.

It is an arithmetic number, because the mean of its divisors is an integer number (448).

It is a Poulet number, since it divides 22820-1.

22821 is an apocalyptic number.

2821 is the 31-st octagonal number.

It is an amenable number.

2821 is a deficient number, since it is larger than the sum of its proper divisors (763).

2821 is a wasteful number, since it uses less digits than its factorization.

2821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51.

The product of its digits is 32, while the sum is 13.

The square root of 2821 is about 53.1130868996. The cubic root of 2821 is about 14.1297462318.

The spelling of 2821 in words is "two thousand, eight hundred twenty-one".

Divisors: 1 7 13 31 91 217 403 2821